Start with this talk from Richard Wilkinson, whose 2009 book The Spirit Level gathers decades of research to draw this conclusion: Societies with more income inequality suffer — in utterly predictable ways — more than societies that are more equal.

For a followup, watch Majora Carter’s classic TEDTalk “Greening the Ghetto” — which shows the effects of income inequality on her home in the South Bronx, and offers triple-bottom-line solutions for raising incomes and reducing environmental damage.

And do not miss Bryan Stevenson’s TEDTalk about economic injustice and its consequences — with a bold call for everyone to look honestly at the problem: “We have a system of justice in [the US] that treats you much better if you’re rich and guilty than if you’re poor and innocent.”